1. Field of the Invention
This invention generally relates to a conversion circuit, and more particularly, to a conversion circuit that discriminates sourcing current and sinking current.
2. Description of the Prior Art
In the field of power source conversion, the use of a conversion circuit in current mode has been focused on outputting current from the conversion circuit to a load, such as so-called sourcing current. However, the one direction output of the above-mentioned conversion circuit cannot meet the needs of modern application circuits. Taking an application circuit of double data rate synchronous dynamic access memory (DDR SDRAM) as an example, the application circuit not only needs the current provided by a conversion circuit, but also needs the current received by the conversion circuit. More particularly, the output of the conversion circuit not only outputs current to the load formed by DDR SDRAM, but also inputs current from the load formed by DDR SDRAM. And, the current flowing from the load to the output of the conversion circuit is so-called sinking current.
As mentioned above, since the traditional conversion circuit in current mode only provides sourcing current but lacks of providing sinking current, the circuit cannot receive the current from the load when the load works in a sinking current mode. Perhaps, the circuit could receive the current from the load but has no the ability of voltage regulation. This situation would make the circuit burned-out or cause abnormal action. Moreover, the conversion circuit for integrating both sourcing and sinking current loads requires two sets of power source designs, one for positive and the other one for negative, so as to offer a positive or a negative referred voltage compared to corresponding feedback signals, respectively. However, the two sets of power source designs not only increase the layout areas in an integrated circuit (IC), but also raise the complexity of the circuit design.
In view of the drawbacks mentioned with the prior art of conversion circuit, there is a continued need to develop a new and improved circuit that overcomes the disadvantages associated with the prior art of conversion. The advantages of this invention are that it solves the problems mentioned above.